Data Manipulation
You can use a business rule each time your application inserts, updates, deletes, or views data. Business rules implemented this way provide concise control over the data that can be updated and how it is updated. For example, if your application applies new sales orders to the invoice file, a business rule should automatically check the customer's credit limit before accepting and inserting the sales order line items.

Validating Data
Data validation is the process of verifying field values (is the numeric field really numeric and within range?) and validating related file values (does the publisher identification exist in the Publishers file?). By putting all of the data validation routines into business rules, your application can guarantee correct data and easily adapt to future requirements. For more information, see Data Validation.

Controlling Data Security
Your application may require access security to control who gets to view and modify your application's data. Security concerns more than just authorizing user logons: security is about controlling access to all of your application's architectural components and data access processes, including:

Handling Multifile Data Access
If your application needs to trace a complex chain of logic and data values as preparation for a decision process, you should use a business rule to simplify the multifile access. Your business rule would automatically find all of the required data structures and repackage them for easy use. For example, suppose your application needs to determine the maximum possible payout for a single procedure in a multiline health care claim. While inspecting the current line item, the beneficiary's entire claim history must be searched for prior use of the identical procedure. Additionally, lifetime and current year-to-date limits must be checked to determine the allowable amount. This kind of multifile data access presents an excellent opportunity to create a reusable business rule that consistently and correctly handles the situation.

Providing Referential Integrity
One of the most common uses for business rules is handling referential integrity. The issue of referential integrity is important for relational as well as indexed files. Because indexed files (such as VSAM) are typically just raw data storage engines, your application must provide custom code to handle constraints, foreign key deletions, and other common referential integrity issues. Application-based referential integrity can also be appropriate for relational databases, especially in situations where the available triggers, constraints, and stored procedures are ...